Gas turbine engines employ high speed bearings that require a continuous supply of oil for lubrication and cooling. For optimum performance, the oil flow must be properly directed into and away from the bearings. Failing to remove or scavenge oil from the bearing can be as detrimental to the bearing as insufficient oil flow because the churning of unscavenged oil within the bearing can rapidly lead to overheating.
In a conventional lubrication system, oil is supplied to the rolling elements of the bearings under pressure and then relies on gravity or its dynamics to drain back to a reservoir. The most effective way to accomplish the return flow is to maintain an open, straight, and unrestricted passageway from the bearing back to the sump. However, in small gas turbine engines such passageways are very difficult to construct because bearing cavities tend to be limited in volume and located in isolated areas within the engine.
As shown in FIG. 5, one approach to this problem has been to integrate the oil return passageway with the bearing liner 8 in the form of axial channels along the liner's outer surface. However, as engines get smaller and operating speeds increase, there is always need for improved lubricant scavenging.